In packaging container producing equipment for producing packaging containers, into which a content is filled, from sheet-like web, rolled sheet-like web W of rewinder 1 is transferred by web feeding roller 10 and is sent to tube forming device 3 via tension pressing device 2 consisting of a dancer roller (rocking roller) 9, which gives tension to the above-mentioned web W at all times, and guide roller 11, wherein the sheet-like web W is formed into tubular web W by multiple stages of forming rollers 14 (only one stage is illustrated in FIG. 1), and the edges overlapped in the lengthwise direction of the tubular web W are sealed (longitudinally sealed) in the longitudinal direction. Furthermore, after a part of web W is sealed (cross-sealed) in the direction orthogonal to the lengthwise direction of web W, a content is filled into the tubular web W located at the upstream side of the cross-sealed part, and after cross sealing is further carried out at a length equivalent to one container in the above-mentioned web, said cross sealed part is cut off, whereby a hexahedral packaging container is produced with the contents filled therein.
The tube forming device 3 is provided with a filling pipe 5 to fill a section of the tube with contents such as fluid food, etc., and is provided with a pair of seal jaws 7 (only one jaw 7 is illustrated in FIG. 1), in order to seal the tubular web W from opposing sides of the tubular web W via a drive mechanism (not illustrated) operated from the main shaft 6 of the packaging container producing equipment.
A pair of cross seal jaws 7 moves downwards while pulling the tubular web W downwards. After the seal jaws 7 move down a predetermined distance, they release the web W to cancel the downward transfer force on the tubular web W and move to separate from each other. Then, the seal jaws 7 are elevated the predetermined distance and repeat their sealing action on the tubular web W again.
As shown in a detailed view (only one of the pairs is illustrated in this drawing) of the cross seal jaws 7 of FIG. 3, the above-mentioned cross seal jaws 7 are provided with jaws 7b attached to a horizontal bar 7a, and web is nipped between a pair of jaws 7b to cause a cross sealing to be executed. Furthermore, lug folding flaps 7c rotating in the direction of the arrow A are attached to one of the cross seal jaws 7, wherein while web W is nipped between a pair of jaws 7b, the above-mentioned lug folding flaps 7c are able to fold lugs Wb formed in the web W.
Specified printing patterns and detection marks a (See FIG. 4), such as a straw port for registering positions are provided at appointed intervals on the web W. Using the position of the above-mentioned detection mark a as reference, it is necessary to adjust the feeding amount of web W (this is called "mark registration") in packaging container producing equipment so that detection marks a of printing surface for each packaging container C come to an appointed position.
However, since errors in positioning of patterns and straw ports when printing on sheet-like web and changes of the feeding amount of web W due to defective rotations of rollers in the packaging container producing equipment are unavoidable, it is necessary to register the above-mentioned marks at all times while the packaging container producing equipment is in operation. If the feeding amount becomes such that it can not be adjusted by registering the above-mentioned marks, there are cases where packaging containers C which are the final formed products can not be formed to their intended shape.
Mark registration is carried out by combination of (1) a method of adjusting the folding amount of web W in its transfer direction and (2) a method of adjusting the degree of tension applied to web W being transferred.
(1) Method of adjusting the folding amount of web W in its transfer direction (See FIG. 11)
The feeding amount of web W in the transfer direction is adjusted in two stages of action, wherein the first action is to adjust the feeding amount of web W in the transfer direction by a pulling force of web W, and the second action adjusts the folding angle of a lug portion formed on web W. By combining these methods, the web W is transferred in the web transfer direction.
The mechanical feeding action of web W in the transfer direction consists of the following two actions shown in FIG. 11.
1 By the sealing part of web W being nipped at both sides by a pair of cross seal jaws 7, the mechanical feeding action is carried out by pulling the web W equivalently to the moving distance of the cross seal jaws 7 in the web transfer direction (See FIG. 11(a)). The drive of a pair of cross seal jaws 7 consisting of two sets is repeated as shown by the arrow R in FIG. 11, wherein a pair of cross seal jaws 7 consisting of two sets repeat this action alternately, web W can be continuously transferred.
2 The shape of web W taken along the line A--A in FIG. 11(a) is as shown in FIG. 11(b), and the lug part web Wb (See FIG. 12) is folded, as shown in FIG. 11 (c), from both sides of tubular web W in the right angle direction with respect to the cross seal part Wa formed by the above-mentioned action (i).
The above-mentioned actions 1 and 2 are basically for applying cross sealing to tubular web W, folding a lug part formed at the cross sealed part and finally forming a hexahedral body. However, by adjusting the folding angle of the lug folding flaps 7c, it is possible to adjust the feeding amount of web W.
(2) Method of adjusting the degree of tension applied to web W being transferred.
In order to accurately move web W only an appointed distance without fail by the method of adjusting the web feeding amount based on adjustment of the folding angle by the lug folding flaps 7c of the above-mentioned action (1), it is necessary give adequate fixed tension to web W by tension pressing device 2 (FIG. 1). For example, if the tension of web W is too much, a mechanical slip occurs between web W and its feeding members, thereby causing the amount of movement of web W to be decreased. To the contrary, if the web tension is too weak, the web is slackened to cause the web W to be transferred beyond that necessity. Thus, appointed tension is given to web W so that the proper amount of web W being transferred is neither too much nor too little.
By combination of this method (2) and the above-mentioned method (1), the mark registration is carried out.
Correction of the amount of feeding is carried out by the lug folding flaps 7c while applying appointed tension to the web for a slight change (for example, 1% of the prescribed value) of the feeding amount of web W. However, the appointed tension control by a tension pressing device was carried out by only the pressing force in the direction of gravity due to the self weight of the dancer roller 9 shown in FIG. 1.
However, if the printing patterns of packaging containers which are the final products slip from their proper positions, the container become worthless. Therefore, it is necessary that a change (error) of the feeding amount of web W, for example, the average error of each time for 100 pitches of web feeding action equivalent to one packaging container C, is less than an appointed value (for example, 0.5 mm or less) and a change (error) of the feeding amount of web per pitch of the web feeding action equivalent to one packaging container C does not exceed an appointed value (for example .+-.1.5 mm).
Furthermore, the more the roll-like web W is consumed, the more frequently occurs a case where a slip of the detection marks in the transfer direction exceeds the permissible range of correction of the mark registration, whereby it becomes impossible to correct the feeding amount of web W.
Thus, in the prior art, since the allowance for the feeding amount of web W is narrow, there was a problem in that it was difficult to adjust the feeding amount of web W with the machine continuously operating.
It is an object of the invention to improve the deficiencies of the prior art.
It is therefore an object of the invention to increase the correctable allowance of error in mark registration of detection marks such as printing patterns on web W.
Furthermore, it is another object of the invention to widen the range for correction of the web feeding amount, so that products do not become defective even though a change (error) in the feeding amount of web W is larger than before.
Furthermore, it is still another object of the invention to provide equipment and a method for producing packaging containers having high quality by increasing the range for adjustment of the feeding amount of web W using, as a reference, the positions of detection marks, which will be signs on the web W, as references.